The present invention relates to a machine for producing frozen beverages, such as water-ices.
In the known art machines have been known which comprise a transparent tank containing an evaporator of a refrigerating circuit and a mixing propeller to keep a beverage moving in the tank and cool it. A delivery tap at one end of the tank enables the frozen beverage thus obtained to be poured out. Usually, the tank is provided with a side opening for sealingly receiving the evaporator and mixer, which are horizontally supported in cantilevered fashion by a vertical shoulder fastened to the machine base. As a result of this, the tank can be easily removed for careful cleaning.
If the beverage is cooled too much, the beverage thickness becomes consequently excessive and there is an increase in the propeller resistance to rotation until the propeller completely stops. Under this condition the electric rotation motor is likely to undergo a permanent damage in a short period of time. In order to avoid this damage, in known machines thermal protection have been inserted which intervene when the motor, due to its stopping, gets overheated; it has also been suggested that the motor should be mounted in such a manner that in case of an excessive resistance to rotation the motor itself will, by reaction, turn about the shaft axis, against the action of a counterspring, thereby activating a microswitch that will disable the refrigerating circuit.
Should the beverage thickness increase too much and in particular should the beverage get fully frozen so as to form a single ice block consisting of several liters in volume, a relatively long time will be required before the beverage thickness may come back to an acceptable value. In addition, in spite of the contemplated solution in which it is waited for motor overheating before proceeding to electrically disconnecting it, an anomalous motor stress is involved which in the long run will bring about failures.
It is also to be pointed out that obviously, except for some fortuitous cases, the motor cooling time does not coincide with the mass thawing time. As a result, the motor could be submitted to repeated overheatings. Passage of the rotating propeller shaft through the tank wall often gives rise to some problems, due both to unavoidable liquid losses and escapes therethrough and to difficulties encountered in cleaning operations.
It is a general object of the present invention to obviate the above mentioned drawbacks by providing a machine for producing frozen beverages which enables the mixture thickness to be brought back to an optimal thickness more quickly in case of an excessive cooling, avoids occurrence of motor overheatings, and prevents liquid losses and problems in cleaning the tank.